The American Civil War was a civil war in the United States fought between northern and Pacific states and southern states that voted to secede and form the Confederate States of America. The central cause of the war was the status of slavery, especially the expansion of slavery into newly acquired land after the Mexican-American War.
After former U.S. Congressman Abraham Lincoln won the November 1860 presidential election on an anti-slavery expansion platform, an initial seven Southern slave states declared their secession from the country to form the Confederacy. War broke out in April 1861 when the Confederate army attacked Fort Sumter in South Carolina, just over a month after Lincoln's inauguration. An additional four slave states joined the Confederacy in the following two months. The Confederacy grew to control at least a majority of territory in those eleven states, and it claimed the additional states of Kentucky and Missouri by assertions from native secessionists fleeing Union authority. These states were given full representation in the Confederate Congress throughout the Civil War.